* {
  margin: 0;
  padding: 0;
}

ul,
ol,
li {
  list-style: none;
}
.box {
  width: 600px;
  height: 400px;
  border: 3px solid black;
  margin: 50px auto;
  display: flex;
  flex-direction: column;
}

.box > ul {
  height: 60px;
  display: flex;
}

.box > ul > li {
  flex: 1;
  background-color: #fff;
  font-size: 20px;
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
}
.box > ul > li.active {
  background-color: pink;
}

.box > ol {
  flex: 1;
  position: relative;
}

.box > ol > li {
  width: 100%;
  height: 100%;
  background-color: pink;
  position: absolute;
  left: 0;
  top: 0;
  font-size: 30px;
  display: none;
}

.box > ol > li.active {
  display: block;
}
